How to do NATIVE PAGE?

Dear Reader!
I want to separate my target protein from other proteins in low
concentration
via native PAGE (poly acrylamide gel electrophoresis).
What do I have to think about when planning the experiment?
Where are the differences between native PAGE and SDS-PAGE?
I heart that one has to calculate the isoelectric point.
But how can I do this with a 300 aa-protein? (the sequence is known)
Thank you for your answer!
Thorsten Schmidt